8.9.6 Using Symbolic Links

You can move databases or tables from the database directory to
other locations and replace them with symbolic links to the new
locations. You might want to do this, for example, to move a
database to a file system with more free space or increase the
speed of your system by spreading your tables to different
disks.

The recommended way to do this is to symlink entire database
directories to a different disk. Symlink
MyISAM tables only as a last resort.